I. Expression of Foreign Protein in Bacterial Cells
An ability to control or regulate the expression of a cloned homologous or heterologous gene in a host cell is a central requirement of recombinant DNA technology. Recombinant molecules capable of mediating the expression of such genes and methods for employing such molecules are described by Cohen et al., U.S. Pat. Nos. 4,237,224 and 4,468,464 and by Maniatis, T. et al., Molecular Cloning (A Laboratory Manual), 2nd edition, Cold Spring Harbor Laboratory, 1989.
Whether expression of the cloned gene is continuous or modulated, when it is desired to express the gene, it is frequently highly desirable to obtain as much of the protein encoded therein as possible.
The amount of a cloned protein which is recovered from a host reflects an equilibrium between the ability of the host to synthesize the protein and the ability of the host to degrade the protein. Often, bacterial hosts degrade foreign, cloned proteins at rates which are much higher than the degradation rate of a homologous host protein. Thus, it is desirable to identify mechanisms that can minimize such degradation.